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13341. 题目: Suction stress characteristics in granite red soils and their relationship with the collapsing gully in south China
文章编号: N18080707
期刊: CATENA
作者: Yusong Deng, Xiaoqian Duan, Shuwen Ding, Chongfa Cai, Jiazhou Chen
更新时间: 2018-08-07
摘要: The main goal of this research is to study the relationship between the soil suction stress and soil properties within four different soil profiles of collapsing gullies in the hilly granitic region of southern China. Large differences were found in the four soil layers between granite red soils, which are manifested in terms of soil bulk density, porosity, particle composition, clay minerals, micromorphology, organic matter, cation exchange capacity, permeability, oxide and hydraulics properties. The suction stress of the upper soils increases rapidly and almost linearly monotonously with the increase of matric suction, whereas C layers increases rapidly first, followed by a slow increase. The suction stress of the lower soils is significantly smaller than the upper soils under the same matric suction. These findings illustrate that the collapsing gully starts from the lower part of the granite red soil, and finally caused the gravity collapse in the upper soils, which is the main aspect that is different from the other types of soil erosion. Furthermore, suction stress has a very significant correlation with soil properties, with a positive correlation to the fine particle content, iron and aluminum oxide, and a negative correlation to coarse particles. In addition, suction stress can also be explained as being directly proportional to weathering degree. Our research provides a theoretical basis for the mass failures of the granite-derived red soil in southern China.

13342. 题目: Dissolved inorganic nitrogen fluxes from common Florida Bay (U.S.A.) sponges
文章编号: N18080706
期刊: Limnology and Oceanography
作者: Daniel R. Hoer, Jake P. Tommerdahl, Niels L. Lindquist, Christopher S. Martens
更新时间: 2018-08-07
摘要: Sponge biomass represents the largest heterotrophic component of benthic biota in the Florida Bay ecosystem. These organisms can significantly alter the water quality of their surrounding environment through biogeochemical transformations of nutrient elements resulting from their dynamic pumping, water filtration, and respiration processes. Ammonium (NH4+) and nitrate plus nitrite (NO3 + NO2; NO x) fluxes were obtained for 11 ecologically important species at three sites within Florida Bay, Florida (U.S.A.) utilizing chamber incubations on undisturbed individual sponges. Significant dissolved inorganic nitrogen (DIN) effluxes ranging between 9.0 ± 2.2 μmol N h−1 Lsponge−1 and 141 ± 26 μmol N h−1 Lsponge−1 were observed for eight of the 11 tested sponges; specifically, from six of eight tested high‐microbial abundance (HMA) sponges, and from two of three tested low‐microbial abundance (LMA) sponges. The abundant HMA species Chondrilla nucula showed the highest, volume‐normalized rate of DIN release. These fluxes represent a continuation of the previously observed dichotomy in the chemical speciation of DIN in exhalent waters of LMA and HMA sponges, with NH4+ and NO x dominating their respective exhalent jets. Surprisingly, we found that dissolved organic matter (DOM) appeared to make a negligible contribution to the total released N, but we hypothesize that the lack of DOM utilization or production was due to methodological limitations. Our flux data combined with sponge biomass estimates indicate that sponges, particularly HMA species, are a large, and potentially dominant, source of inorganic nitrogen to Florida Bay waters.

13343. 题目: Combined effects of nitrogen fertilizer and straw application on aggregate distribution and aggregate‐associated organic carbon stability in an alkaline sandy loam soil
文章编号: N18080705
期刊: European Journal of Soil Science
作者: Z. Wang, Z. Wang, L. J. Ma, W. A. Khattak, W. Hu, Y. L. Meng, Z. G. Zhou
更新时间: 2018-08-07
摘要: Research on aggregate‐associated organic carbon (AOC) stability has increased, but its response to nitrogen (N) and straw (S) application after nitrogen reduction in alkaline sandy loam soil remains unclear. A two‐year field study and a short‐term incubation experiment were performed to investigate the combined effect of the N+S application on aggregate distribution and stability, and AOC content and mineralization in eastern China. The study involved three N amounts (75, 150 and 300 kg N ha‐1) with or without straw amendments under continuous cotton–barley rotation. The N+S application promoted the formation of larger macroaggregates (8–2 mm), with larger mean weight diameter and geometric mean diameter than with N application alone. Aggregate stability increased significantly with increasing rate of N application. The amount of N had less effect on AOC content in the 0–20‐cm layer and cumulative mineralization of AOC in both layers compared to the N+S application. The addition of straw in promoting AOC, however, was more evident in the 20–40‐cm layer. Compared with N fertilizer alone, applying N+S increased the cumulative mineralization of AOC by 27.7 % in the 0–20‐cm layer and by 80.9 % in the 20–40‐cm layer for different rates of N and aggregate sizes. In addition, at 0–20‐cm depth, there was less C mineralization in macroaggregates than in microaggregates, indicating that macroaggregates showed better protection of AOC in that layer. Our study suggests that N application alone had a large effect on aggregate stability, whereas combined N+S application had a large effect on AOC content and its mineralization in the soil studied.

13344. 题目: Pollutant transport analysis and source apportionment of the entire non-point source pollution process in separate sewer systems
文章编号: N18080704
期刊: Chemosphere
作者: Yukun Ma, Shaonan Hao, Hongtao Zhao, Jinxiu Fang, Jiang Zhao, Xuyong Li
更新时间: 2018-08-07
摘要: Understanding pollutant transport process and source apportionment is critical to urban stormwater pollution mitigation. Previous studies have investigated transport and sources of road deposited sediments (RDS) and sewer sediments individually, and most of these studies focused on stormwater pollution in combined sewer systems. However, studies about pollutant transport and source apportionment of the entire urban non-point source pollution process in separate sewer systems are lacking. This study analyzed particle size distribution and chemical pollutants in five media during the entire pollutant process including RDS, roof runoff, road runoff, sewer sediments, and sewer runoff. The outcomes found that mass percentage of fine particles became greater during pollutant transport in stormwater runoff. According to transport characteristics, particles were grouped into three types: particles <20 μm, 20–105 μm, and >105 μm. Particles <20 μm had the highest mobility capacity and particles >105 μm had the lowest mobility capacity, while mobility capacity of particles 20–105 μm was uncertain. Pollutant concentrations in road runoff were significantly influenced by rainfall intensity and pollutant concentrations in sewer runoff could become lower during rainy seasons ignoring rainfall intensity. RDS was the main contributor of heavy metals while organic matter and nutrients were primarily contributed by sewer sediments. Roof runoff, road runoff and sewer sediments contributed 5.35%, 69.24% and 25.41% particles to urban receiving water, respectively. Based on the outcomes, several suggestions were given for stormwater management.
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13345. 题目: Influence of inherent hierarchical porous char with alkali and alkaline earth metallic species on lignin pyrolysis
文章编号: N18080703
期刊: Bioresource Technology
作者: Shaoqing Wang, Zhihe Li, Xueyuan Bai, Weiming Yi, Peng Fu
更新时间: 2018-08-07
摘要: This study aimed to explore the influence of inherent hierarchical porous char with alkali and alkaline earth metallic species (AAEMs) during pyrolysis of lignin derived from agricultural crop residues in a laboratory fixed-bed at 550 °C. A catalytic strategy was implemented to investigate volatile-char interactions based on ex situ lignin pyrolysis. The physico-chemical properties of the AAEMs-loaded char were characterized by FTIR, XRD, SEM-EDX and N2 nitrogen adsorption analyses. Results indicated that AAEMs-loaded char had a large specific surface area, hierarchical porosity, amorphous carbon structure, surface-active functional groups and highly dispersed metal species. Specifically, the specific surface area of AAEMs-loaded char was significantly reduced owing to coke deposition after interaction with pyrolysis vapours. Bio-oil composition revealed substantial increases in phenol, o-cresol, p-cresol and catechol. These increases were mainly attributed to demethylation, demethoxylation, or alkyl substitution reaction. The experimental results confirmed the occurrence of significant volatile-char interactions during lignin pyrolysis.
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13346. 题目: Mechanistic insights into sequestration of U(VI) toward magnetic biochar: Batch, XPS and EXAFS techniques
文章编号: N18080702
期刊: Journal of Environmental Sciences
作者: Qingyuan Hu, Yuling Zhu, Baowei Hu, Songhua Lu, Guodong Sheng
更新时间: 2018-08-07
摘要: The magnetic iron oxide (Fe3O4) nanoparticles stabilized on the biochar were synthesized by fast pyrolysis of Fe(II)-loaded hydrophyte biomass under N2 conditions. The batch experiments showed that magnetic biochar presented a large removal capacity (54.35 mg/g) at pH 3.0 and 293 K. The reductive co-precipitation of U(VI) to U(IV) by magnetic biochar was demonstrated according to X-ray diffraction, X-ray photoelectron spectroscopy and X-ray absorption near edge structure analysis. According to extended X-ray absorption fine structure analysis, the occurrence of U-Fe and U-U shells indicated that high effective removal of uranium was primarily inner-sphere coordination and then reductive co-precipitation at low pH. These observations provided the further understanding of uranium removal by magnetic materials in environmental remediation.
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13347. 题目: Heteroaggregation and sedimentation of graphene oxide with hematite colloids: Influence of water constituents and impact on tetracycline adsorption
文章编号: N18080701
期刊: Science of The Total Environment
作者: Yiping Feng, Khanh An Huynh, Zhijie Xie, Guoguang Liu, Shixiang Gao
更新时间: 2018-08-07
摘要: Because the transport of graphene oxide nanosheets (GO) from water to sediments is influenced by their heteroaggregation and sedimentation with natural colloids, knowledge on the interdependence of heteroaggregation and sedimentation for GO is needed to gain a better insight on the environmental fate of these nanosheets. However, this phenomenon is still not well understood. In this study, the heteroaggregation and sedimentation behaviors of GO with hematite nanoparticles (HemNPs) were investigated at various conditions. It has been found that negatively charged GO rapidly underwent heteroaggregation with positively charged HemNPs, leading to the sedimentation of GO. Significant sedimentation occurred when the net charge of the GOHemNP mixture was close to zero. The presence of various natural organic matters suppressed the sedimentation of the heteroaggregates through various mechanisms. Specifically, adsorption of humic acid and alginate reversed HemNP surface charge from positive to negative, leading to a slow sedimentation of the GOHemNP mixtures due to the increase in nanoparticle electrostatic repulsion. Adsorption of bovine serum albumin raised steric hindrance effect between GO and HemNP, which in turn inhibited their heteroaggregation and sedimentation. At high ionic strength conditions, the sedimentation of GO and HemNP was enhanced, possibly through the combination of homo- and hetero-aggregation. At elevated pH, the heteroaggregates were partially disaggregated, probably due to the weakening of GOHemNP bonds as the surface charges of these nanomaterials became more negative. Moreover, heteroaggregation of GO with HemNP likely to occupy the adsorption sites on GO surfaces, thus greatly reduced the adsorption of tetracycline on GO. These findings highlighted the important roles of natural colloids on the fate and transport of GO, together with the importance of heteroaggregation on the adsorption of co-existing pollutants to GO in natural aquatic environments.
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13348. 题目: Microbes follow Humboldt: temperature drives plant and soil microbial diversity patterns from the Amazon to the Andes
文章编号: N18080609
期刊: Ecology
作者: Andrew T. Nottingham, Noah Fierer, Benjamin L. Turner, Jeanette Whitaker, Nick J. Ostle, Niall P. McNamara, Richard D. Bardgett, Jonathan W. Leff, Norma Salinas, Miles Silman, Loeske Kruuk, Patrick Meir
更新时间: 2018-08-06
摘要: More than 200 years ago, Alexander von Humboldt reported that tropical plant species richness decreased with increasing elevation and decreasing temperature. Surprisingly, co-ordinated patterns in plant, bacterial and fungal diversity on tropical mountains are yet to be observed, despite the central role of soil microorganisms in terrestrial biogeochemistry. We studied an Andean transect traversing 3.5 km in elevation to test whether the species diversity and composition of tropical forest plants, soil bacteria and fungi follow similar biogeographical patterns with shared environmental drivers. We found co-ordinated changes with elevation in all three groups: species richness declined as elevation increased, and the compositional-dissimilarity among communities increased with increased separation in elevation, although changes in plant diversity were larger than in bacteria and fungi. Temperature was the dominant driver of these diversity gradients, with weak influences of edaphic properties, including soil pH. The gradients in microbial diversity were strongly correlated with the activities of enzymes involved in organic matter cycling, and were accompanied by a transition in microbial traits towards slower-growing, oligotrophic taxa at higher elevations. We provide the first evidence of co-ordinated temperature-driven patterns in the diversity and distribution of three major biotic groups in tropical ecosystems: soil bacteria, fungi and plants. These findings suggest that inter-related patterns of plant and microbial communities with shared environmental drivers occur across landscape scales of relatively constant soil pH, with implications for tropical forest communities under future climate change.

13349. 题目: Variation in hydrogen isotope composition among saltmarsh plant organic compounds highlights biochemical mechanisms controlling biosynthetic fractionation
文章编号: N18080608
期刊: Journal of Geophysical Research: Biogeosciences
作者: Yvette Eley, Joseph White, Lorna Dawson, Michael Hren, Nikolai Pedentchouk
更新时间: 2018-08-06
摘要: Hydrogen isotopes of plant‐derived biomarkers can vary by >100‰ at a single location. Isotope fractionation associated with the movement of water in plant leaves cannot account for this variability alone. Biochemical processes therefore must play a fundamental role in controlling hydrogen isotope fractionation during secondary compound biosynthesis. Different biosynthetic pathways utilize discrete hydrogen pools, and occur within distinct cell compartments. We analysed hydrogen isotope compositions of C16 and C18 fatty acids and phytol from 7 saltmarsh plants, and compared these data with: (i) leaf water and n‐alkane δ2H; (ii) leaf carbon and nitrogen contents; and (iv) nitrogen isotopes of bulk tissue, to evaluate the relationship between biochemical processes, cellular compartmentalization, and hydrogen isotope fractionation. Interspecies variation in chloroplastic fatty acids and phytol δ2H exceeds leaf water δ2H, indicating that different commitments of metabolites among species at branching points in chloroplast metabolic processes may be important determinants of lipid δ2H values. Dominant osmoregulatory strategies, in particular, show strong correlation with leaf wax n‐alkane δ2H. Species that preferentially produce nitrogenous compounds (dicots/shrubs) as protective solutes have 2H‐enriched n‐alkanes relative to species that produce mainly carbohydrates (monocots). n‐Alkane δ2H values, in combination with δ15N data and elemental (C, N) composition, together provide information about biochemical environmental adaptations exhibited by different higher plant species in response to environmental stresses. Thus, while spatial and temporal integration of biomarkers may produce an isotopic record of ecosystem function, biomarkers from individual plant or microbial remains may hold additional details into biologic function and adaptation to ancient environments.

13350. 题目: Effects of straw management and nitrogen application rate on soil organic matter fractions and microbial properties in North China Plain
文章编号: N18080607
期刊: Journal of Soils and Sediments
作者: Zengqiang Li, Dandan Li, Lei Ma, Yueyue Yu, Bingzi Zhao, Jiabao Zhang
更新时间: 2018-08-06
摘要: Purpose: A 2-year field experiment was conducted on the North China Plain to assess the effects of two straw management practices and different nitrogen fertilizer addition levels on soil organic matter (SOM) fractions and microbial properties under a winter wheat-summer maize cropping system. Materials and methods: Eight treatments (two straw management practices and four nitrogen fertilizer input levels) were established using a randomized complete block design. The straw management practices were no straw return and straw return. Each straw management practice received nitrogen fertilizer rates at 0 (N0), 270 (N270), 360 (N360), or 450 (N450) kg N ha−1 year−1. The soil properties measured included SOM fractionation, enzyme activities, community level physiology profile (CLPP), and microbial community abundance and composition, which were represented by phospholipid fatty acid (PLFA). Results and discussion: Compared to no straw return, the addition of straw significantly increased soil total organic carbon and nitrogen, particulate organic carbon and nitrogen, and occluded particulate organic carbon and hot water extractable organic carbon by 7–29%. Invertase, protease, urease, and dehydrogenase activities increased by 22–40%. The biomasses of Gram-positive bacteria and fungi also increased. The increase in SOM fractions may be attributed to the decomposition of the added straw by more active enzymes, which may result from the shift of microbial community composition. In addition, hot-water extractable organic carbon, NO3-N, urease activity, and fungal biomass in the N270, N360, and N450 treatments significantly increased, independent of the nitrogen application rate, which indicated that N input level had a non-linear effect on soil properties in this area. Conclusions: Short-term straw return combined with a modest nitrogen fertilizer input (270 kg N ha−1 year−1) can increase SOM contents and microbial activity, which may help improve soil fertility in this region.

13351. 题目: Abundance of lipids in differently sized aggregates depends on their chemical composition
文章编号: N18080606
期刊: Biogeochemistry
作者: Gerrit Angst, Klaas G. J. Nierop, Šárka Angst, Jan Frouz
更新时间: 2018-08-06
摘要: Evidence for a vital role of soil mineral matrix interactions in lipid preservation is steadily increasing. However, it remains unclear whether solvent-extractable (‘free’) or hydrolyzable (‘bound’) lipids, including molecular proxies, e.g., for cutin and suberin, are similarly affected by different stabilization mechanisms in soil (i.e., aggregation or organo-mineral association). To provide insights into the effect of these stabilization mechanisms on lipid composition and preservation, we investigated free and bound lipids in particulate and mineral soil fractions, deriving from sand- and silt-/clay-sized aggregates from a forest subsoil. While free lipids accumulated in sand-sized aggregates, the more complex bound lipids accumulated in silt- and clay-sized aggregates, particularly in the respective mineral fractions < 6.3 µm (fine silt and clay). The presence of both, cutin and suberin markers indicated input of leaf- and root-derived organic matter to the subsoil. Yet, our cutin marker (9,10,ω-trihydroxyoctadecanoic acid) was not extracted from the mineral aggregate compartments < 6.3 µm, perhaps due to its chemical structure (i.e., cross-linking via several hydroxy groups, and thus higher ‘stability’, in macromolecular structures). Combined, these results suggest that the chemical composition of lipids (and likely also that of other soil organic matter compounds) governs interaction with their environment, such as accumulation in aggregates or association with mineral soil compartments, and thus indirectly influences their persistence in soil.

13352. 题目: Influence of soil porewater properties on the fate and toxicity of silver nanoparticles to Caenorhabditis elegans
文章编号: N18080605
期刊: Environmental Toxicology and Chemistry
作者: Carolin L. Schultz, Elma Lahive, Alan Lawlor, Alison Crossley, Victor Puntes, Jason M. Unrine, Claus Svendsen, David J. Spurgeon
更新时间: 2018-08-06
摘要: Engineered nanoparticles (NPs) entering the environment are subject to various transformations that in turn influence how particles are presented to, and taken up by, organisms. To understand the effect of soil properties on the toxicity of nanosilver to Caenorhabditis elegans, toxicity assays were performed in porewater extracts from natural soils with varying organic matter content and pH using 3–8 nm unfunctionalized silver (Ag 3–8Unf), 52‐nm polyvinylpyrrolidone (PVP)‐coated Ag NPs (Ag 52PVP), and AgNO3 as ionic Ag. Effects on NP agglomeration and stability were investigated using ultraviolet‐visible (UV‐vis) spectroscopy and asymmetric flow field‐flow fractionation (AF4); Ag+ showed greater overall toxicity than nanosilver, with little difference between the NP types. Increasing soil organic matter content significantly decreased the toxicity of Ag 3–8Unf, whereas it increased that of AgNO3. The toxicity of all Ag treatments significantly decreased with increasing porewater pH. Dissolution of both NPs in the porewater extracts was too low to have contributed to their observed toxic effects. The UV‐vis spectroscopy revealed low levels of agglomeration/aggregation independent of soil properties for Ag 3–8Unf, whereas higher organic matter as well as low pH appeared to stabilize Ag 52PVP. Overall, both soil organic matter content and pH affected NP fate as well as toxicity to C. elegans; however, there appears to be no clear connection between the measured particle characteristics and their effect. Environ Toxicol Chem 2018;9999:1–10. © 2018 SETAC

13353. 题目: Variations in river input of iron impact sedimentary phosphorus burial in an oligotrophic Baltic Sea estuary
文章编号: N18080604
期刊: Biogeosciences
作者: Wytze K. Lenstra, Matthias Egger, Niels A. G. M. van Helmond, Emma Kritzberg, Daniel J. Conley, and Caroline P. Slomp
更新时间: 2018-08-06
摘要: Estuarine sediments are key sites for removal of phosphorus (P) from rivers and the open sea. Vivianite, an iron (Fe)(II)-P mineral, can act as a major sink for P in Fe-rich coastal sediments. In this study, we investigate the burial of P in the Öre Estuary in the northern Baltic Sea. We find much higher rates of P burial at our five study sites (up to ~0.145molm−2yr−1) when compared to more southern coastal areas in the Baltic Sea with similar rates of sedimentation. Detailed study of the sediment P forms at our site with the highest rate of sedimentation reveals a major role for P associated with Fe and the presence of vivianite crystals below the sulfate methane transition zone. By applying a reactive transport model to sediment and porewater profiles for this site, we show that vivianite may account for up to 40% of total P burial. With the model, we demonstrate that vivianite formation is promoted in sediments with a low bottom water salinity and high rates of sedimentation and Fe oxide input. While high rates of organic matter input are also required, there is an optimum rate above which vivianite formation declines. Distinct enrichments in sediment Fe and sulfur at depth in the sediment are attributed to short periods of enhanced riverine Fe and organic matter input linked to variations in rainfall on land. Most of the P associated with the Fe in the sediment is likely imported from the adjacent eutrophic Baltic Proper. Our work demonstrates that variations in land-to-sea transfer of Fe may act as a key control on burial of P in coastal sediments. Ongoing climate change is expected to lead to a decrease in bottom water salinity and contribute to continued high inputs of Fe oxides from land, further promoting P burial as vivianite in the coastal zone of the northern Baltic Sea. This may enhance the role of this oligotrophic area as a sink for P imported from eutrophic parts of the Baltic Sea.

13354. 题目: Seasonal trends in surface pCO2 and air‐sea CO2 fluxes in Apalachicola Bay, Florida from VIIRS ocean color
文章编号: N18080603
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ishan D. Joshi, Nicholas D. Ward, Eurico J. D'Sa, Christopher L. Osburn, Thomas S. Bianchi, Diana Oviedo‐Vargas
更新时间: 2018-08-06
摘要: Estuaries have been recognized as important sources of carbon dioxide (CO2) to the atmosphere; however, contributions of these systems to regional and global carbon budgets are not well constrained due to limited information on seasonal and spatial variability. In this study, we use satellite remote sensing to obtain seasonal pCO2 distribution and air‐sea CO2 fluxes in Apalachicola Bay, a national estuarine research reserve located in the northern Gulf of Mexico, that receives seasonally varying dissolved organic matter‐rich waters from the Apalachicola River. A combination of time‐series (2005–2016) and seasonal field observations (2015–2016) of pH and biophysical variables were used to develop seasonal pH–pCO2 relationships for obtaining surface pCO2 estimates and air‐sea CO2 fluxes from VIIRS ocean color data. Monthly and seasonal maps of pCO2 and air‐sea CO2 fluxes showed a general trend of higher fluxes in winter and summer corresponding to high river flow and warm water temperatures. However, CO2 fixation via photosynthesis and low water temperatures contributed to lower fluxes to the atmosphere in spring and fall, respectively. Throughout the study period, Apalachicola Bay was a net source of CO2 with large seasonal and spatial variability and a mean annual CO2 flux to the atmosphere of 3.4 ± 3.1 mol m‐2 y‐1 (9.4 ± 8.5 mmol m‐2 d‐1), consistent with fluxes reported for other estuaries. This study demonstrates the critical role that satellite observations can play to improve the estuarine contributions to the global carbon flux estimates.

13355. 题目: The Role of Ligninolytic Enzymes Laccase and a Versatile Peroxidase of the White‐Rot Fungus Lentinus tigrinus in Biotransformation of Soil Humic Matter: Comparative in vivo Study
文章编号: N18080602
期刊: Journal of Geophysical Research: Biogeosciences
作者: A. G. Zavarzina, A. V. Lisov, A. A. Leontievsky
更新时间: 2018-08-06
摘要: Soil organic matter (SOM) turnover by ligninolytic fungi is a large‐scale process that controls organic carbon geochemistry in terrestrial ecosystems. However, the role of certain oxidative enzymes (e.g. laccase) in humus degradation remain unclear, as well as the molecular structure and recalcitrance of SOM components. In order to address these questions, the degradation of forest soil humic acid (HA) in the presence of laccase and a versatile peroxidase (VP) have been studied in the liquid culture of Lentinus tigrinus. Contrary to the evolving views on humus structure, we have found that alkali‐extractable and acid‐insoluble constituents of SOM (HA) contain true macromolecular components, stable in the presence of 0.1% sodium dodecyl sulfate but degradable/re‐synthesizable by oxidative enzymes acting on covalent linkages. The HA degradation in the presence of laccase (high N medium) occurs at slower initial rate than in the presence of VP (low N medium). However each of the enzymes caused about 60% color loss and almost complete degradation of HA into smaller molecules (gel‐filtration data) within two weeks of cultivation. Depolymerization of HA in the culture liquid in the presence of laccase was accompanied by polymerization of degradation products on mycelium. Our results show that 1) humus macromolecules are not stable to oxidative enzymes once desorbed from the mineral phase; 2) laccase of L.tigrinus is comparable by its degradation potential to VP; 3) interfacial secondary synthesis reactions occur during humus decay in the presence of laccase. Our results highlight the important role of laccases in SOM sequestration in soils.

13356. 题目: Organic matter protection by kaolinite over bio-decomposition as suggested by lignin and solvent-extractable lipid molecular markers
文章编号: N18080601
期刊: Science of The Total Environment
作者: Fangfang Li, Zhaofeng Chang, Kaythi Khaing, Yuwei Zhou, Haiyun Zhao, Ni Liang, Dandan Zhou, Bo Pan, Christian E.W. Steinberg
更新时间: 2018-08-06
摘要: The formation of organo-mineral complexes is essential in organic matter (OM) stabilization. However, limited studies have been conducted to systematically examine the mineral influence on the decomposition of plant residuals at a molecular level. In this study, pine needles and chestnut leaves were mixed with kaolinite at the weight ratio of 5:1. The controls were plant tissues without kaolinite. All the samples were incubated in the laboratory for one year. Molecular markers, including lignin-derived phenols (e.g. Vanilly units, syringyl units and cinnamyl units) and solvent-extractable lipids (e.g. n-alkanoic acid, n-alkanols and n-alkanes), were analyzed. The concentrations of lignin-derived phenols and lipid compounds were higher in the presence of kaolinite than without kaolinite. Lower degradation indexes, such as (Ad/Al)V (ratio of vanillic acid to vanillin) and CPI (carbon preference index of n-alkanoic acid and n-alkanes), were found in the kaolinite system. These results indicate that kaolinite reduced the OM decomposition. The addition of kaolinite also stabilized some carbohydrates from plants. Furthermore, the degradation of OM led to the generation of persistent free radicals, indicated by electron paramagnetic resonance (EPR) signals. The EPR signals were higher with than without kaolinite. We hypothesize that the adsorption of semiquinone or quinone radicals on kaolinite may limit their reaction with other OM moieties and thus extended their lifetimes. In addition to embedding OM in soil aggregates, our results provide direct evidence of another mineral protective mechanism of soil OM.
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13357. 题目: Fe–colloid cotransport through saturated porous media under different hydrochemical and hydrodynamic conditions
文章编号: N18080505
期刊: Science of The Total Environment
作者: Xiaofei Li, Wenjing Zhang, Yunqi Qin, Tianyi Ma, Jingjing Zhou, Shanghai Du
更新时间: 2018-08-05
摘要: To investigate the effect of different colloids on Fe migration in saturated porous media under different hydrochemical and hydrodynamic conditions, experiments were performed using colloidal silicon (inorganic) and colloidal humic acid (HA, organic), which are representative of the colloids in groundwater. Transport of Fe with and without colloid was investigated by column experiments using various porous media, colloid concentrations, ionic strengths (ISs), cation valences, and flow rates. The results show that colloidal silicon promotes and colloidal HA inhibits Fe transport, which is mainly because of their different bonding ratio, bonding modes with Fe and opposite surface charges between Fe–colloidal silicon and Fe–colloidal HA. Almost 100% of HA binds to Fe through the deprotonated functional groups, whereas only 13.3% of colloidal silicon binds to Fe, which is by electrostatic forces. Cotransport is also dependent on the hydrochemical and hydrodynamic conditions. For the Fe–colloidal silicon system, increasing the colloid concentration and flow rate, and decreasing the IS enhances Fe transport. Compared with colloidal silicon concentration = 10 mg/L, flow rate = 0.25 mL/min, and IS = 0.05 with CaCl2, a higher colloidal silicon concentration (20 mg/L), a higher flow rate (0.50 mL/min), and a lower IS (<0.0005 M) increase Fe recovery by 1.69%, 94.49% and 38.92%, respectively. Fe migration is also different in different porous media. For the Fe–colloidal HA system, Fe recovery decreases by 81.46% as the colloidal HA concentration increases from 0 to 20 mg/L. The type of porous medium and flow rate conditions have the same effects on Fe–colloidal HA transport as for colloidal silicon, although the electrical conditions have the opposite effect. With increasing IS, Fe–colloidal HA transport is enhanced because of competitive adsorption of the cations and Fe to colloidal HA and the porous medium.
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13358. 题目: Comparative characterization of surface sludge deposits from fourteen French Vertical Flow Constructed Wetlands sewage treatment plants using biological, chemical and thermal indices
文章编号: N18080504
期刊: Science of The Total Environment
作者: M. Kania, M. Gautier, A. Imig, P. Michel, R. Gourdon
更新时间: 2018-08-05
摘要: Due to their design and mode of operation, French Vertical Flow Constructed Wetlands (VFCWs) accumulate suspended solids from the inflow wastewater in the form of a sludge layer at the surface of the first filter. In order to maintain the treatment performance over the long term, the characteristics of the sludge deposits and their evolution have to be well described. In this objective, a panel of sludge deposit samples taken from 14 French VFCW sewage treatment plants was investigated. Elemental composition and organic matter content, nature and reactivity were analyzed. Results clearly revealed two categories of sludge deposits, namely the “young-age plants” type (1 year of operation and less) and the “mature plants” type (3 years of operation and more). Sludge deposits from the “mature plants” exhibited same biological, physical and chemical properties. Their organic matter was globally less abundant, more humified and less biodegradable than in the young-age plants type. Their overall contents in trace metals were also higher, although in a limited manner. The effect of additional treatments, particularly FeCl3 injection for phosphorus precipitation, was observable in the “young-age plants” group. Finally, the sludge deposits sampled from one particular plant with specific operating conditions were found to exhibit very different characteristics from those of either groups identified. This observation underlined the influence of local conditions on the typology of the sludge deposits.
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13359. 题目: Duxite - fossil resin of Miocene age
文章编号: N18080503
期刊: Organic Geochemistry
作者: Martina Havelcová, Vladimír Machovič, Ivana Sýkorová, Ladislav Lapčák, Alexandra Špaldoňová, Karel Mach, Zdeněk Dvořák
更新时间: 2018-08-05
摘要: A series of Miocene fossil resin from the northwest part of the Czech Republic, called duxite, has been analyzed by elemental, microscopic, gas chromatography (GC/MS), pyrolysis-gas chromatography, Fourier Transform infrared (FTIR), and Raman techniques. The set of samples consisted of museum, contemporary and artificially altered samples. The results of GC/MS revealed fine variances in chemical structure among the samples, which could be attributed to the geologic paleosituation during resin deposition, as was verified by alteration of a sample under different conditions. Sesquiterpenes, including α-cedrene and cuparene, were identified in sample extracts and sample pyrolysates together with diterpenoid members abietanes, pimaranes, and dehydroabietanes. The distribution and intensity of functional groups of FTIR spectra also confirmed that the duxite samples were fossilised exudates from a member of the Cupressaceae conifer family. Raman spectra supported this record indicating aromatic character of duxite and higher maturity of the samples.. The chemical composition indicated that duxite is a member of Class IV resins of the fossil resin classification system. Members of this group do not have a polymeric structure. This nonpolymerizable behaviour was confirmed by their excellent solubility in an organic solvent and the low softening point of the material. Our results therefore provide a valuable insight into the duxite-producing process and its potential for evaluating the geological environment and diagenetic conditions.

13360. 题目: Influence of biochars on the accessibility of organochlorine pesticides and microbial community in contaminated soils
文章编号: N18080502
期刊: Science of The Total Environment
作者: Neelum Ali, Sardar Khan, Yaying Li, Ningguo Zheng, Huaiying Yao
更新时间: 2018-08-05
摘要: Biochar can be used as a promising potential substance to reduce the availability of toxic elements and compounds in contaminated soils but its effects on the accessibility of pesticides and microbiological interactions still remain unclear. Here, 65 day incubation experiments were conducted to investigate the efficacy of biochars on the accessibility of 21 different organochlorine pesticides (OCPs), and also to evaluate their influence on soil microbial community. The tested soil was collected from an agricultural field, containing loamy sand texture, and historically contaminated with high concentrations of OCPs. The soil was amended with four different kinds of biochars: sewage sludge biochar (SSBC), peanut shells biochar (PNBC), rice straw biochar (RSBC), and soybean straw biochar (SBBC). The results indicated that biochar-amendments had strong effects upon OCP accessibility over time and can act as super sorbent. Despite greater persistence of OCPs in soil, the application of selected biochars significantly (p < 0.01) reduced the accessibility of ∑OCPs in the amended soil in the order of SSBC (8–69%), PNBC (11–75%), RSBC (6–67%), and SBBC (14–86%), as compared to the control soil during 0–65 d incubation period. Moreover, the findings from total phospholipid acid (PLFA) and Illumina next-generation sequencing revealed that the incorporation of biochar have altered the soil microbial community structure over time. Higher abundances of Proteobacteria, firmicutes, Gemmatimonadetes, and Actinobacteria were found in biochar amendments. However, the relative abundances of Acidobacteria and Chloroflexi decreased, following biochar addition. The findings of these experiments suggest that biochar addition to soil at the rate of 3% (w/w) could be advantageous for decreasing accessibility of OCPs, enhancing the soil microbial communities, and their subsequent risk to environment and food chain contamination.
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